A memorial service will be held on Wednesday, Dec. 4, for Dr. Orvan W. Hess, clinical professor emeritus of obstetrics and gynecology and a fellow of Morse College, who died Sept. 6 at the age of 96 after a short illness.

The service will be held at 11 a.m. at Spring Glen Church, corner of Whitney Avenue and Glendower Road in Hamden. A reception will follow the service.

Dr. Hess pioneered the development of the fetal heart monitor and was instrumental in the first successful clinical use of penicillin in the early 1940s.

A native of Margaretville, New York, Dr. Hess came to Yale-New Haven Hospital in the 1930s after completing his undergraduate degree at Lafayette College, his M.D. at the University of Buffalo and an internship at Children's Hospital in Buffalo, New York. Also a research fellow at the School of Medicine, he began work on a way to measure fetal heart activity. His work was interrupted by World War II, when Dr. Hess served as a surgeon in the front-line hospital attached to General George S. Patton's Second Armored Division in the invasions of North Africa, Sicily and Normandy.

After the war, Dr. Hess returned to Yale and continued his work developing a fetal monitor. The first, a six-and-one-half-foot-tall machine, was introduced in 1957. Dr. Hess and a Yale colleague were the first to detect and record electrical cardiac signals. Throughout the 1960s, Dr. Hess continued to improve his design of the machine, making it smaller and introducing telemetry.

"Other than ultrasound, it is probably the most widely used technique in all of obstetrics," said Dr. Joshua Copel, a Yale professor of obstetrics, gynecology and pediatrics, in The New York Times obituary for Dr. Hess. "Before these monitors were invented, the uterus was literally a black box. We knew the babies were in there, and they came out."

In 1942, Dr. Hess helped save a dying obstetrics patient who had scarlet fever. He mentioned to the woman's internist an article he read about the use of certain antibiotics to kill infections in animals. This prompted the internist to consult with some colleagues who were studying penicillin and to obtain some for the patient. The woman went on to live until she was 90 years old.

For his work, Dr. Hess was honored with the Scientific Achievement Award from the American Medical Association. He was president of the Connecticut State Medical Society and served as director of health services for the Connecticut Welfare Department in the early days of Medicaid and Medicare.

Dr. Hess was predeceased by his wife, the former Carol Maurer, who died in 1998. He is survived by two daughters, Dr. Katherine Halloran of Lexington, Massachusetts, and Carolyn Westerfield (Mrs. H. Bradford Westerfield) of Hamden; five grandchildren; and five great-granddaughters.